1. Filed of the Invention
The present invention relates to a driving mechanism, an imaging mechanism and a cellular phone provided with the driving mechanism, and, in particular, to a driving mechanism for driving a zoom lens and a focus lens of a camera, an imaging mechanism and a cellular phone provided with the driving mechanism.
2. Description of the Related Art
There is available an actuator in which a piezoelectric element is used as a driving mechanism for a lens part of a digital camera and the like. For example, in the actuator disclosed in Japanese Patent No. 2633066, a driving bar is fastened to the front end surface of a piezoelectric element in the elongating and contracting direction and the rear end surface of the piezoelectric element is fixed to the body of a mechanism. The driving bar is supported in a state that a holding frame of a lens is allowed to slide and the holding frame is urged by a blade spring to make a frictional engagement with the driving bar. An approximately serrate driving pulse is applied to the piezoelectric element, by which the piezoelectric element is deformed in the elongating and contracting direction at a different speed. For example, when the piezoelectric element is deformed slowly, the holding frame moves together with the driving bar. In contrast, when the piezoelectric element is deformed quickly, the holding frame remains at the same position due to inertia of the mass. Therefore, the lens is allowed to move intermittently at a fine pitch on a repeated application of the approximately serrate driving pulse to the piezoelectric element.
However, the related-art actuator has such a problem that in order to prevent the displacement of the rear end surface of a piezoelectric element, the rear end surface must be firmly fixed to the body of a mechanism, which results in a larger size of the mechanism due to the fixture.
Further, there is a method in which, instead of fixing the rear end surface of the piezoelectric element, a weight member is attached to the rear end surface, thereby preventing the rear end surface from being displaced to a greater extent than the front end surface. However, according to the method, a weight member must be provided separately and also rigidly coupled to the piezoelectric element, which is a problem.